A new drug for breast cancer which extends women's lives by almost six months is to be blocked from routine NHS access under draft guidance issued by a health watchdog.

Kadcyla, manufactured by Roche, can cost more than £90,000 per patient and is not effective enough to justify the price the NHS is being asked to pay, the National Institute for Health and Care Excellence (Nice) said.

The watchdog, which decides which new medicines are cost effective, said its guidance for Kadcyla, manufactured by Roche, or trastuzumab emtansine, was in draft form and is now up for public consultation.

Meawhile patients will be able to apply to their local NHS and to the Cancer Drugs Fund (CDF) for the drug, a Nice spokeswoman said.

But the decision, if made final later this year, would mean the drug would not be recommended for routine use in England on the NHS and women would have to rely on their doctors' successful application to the Cancer Drugs Fund.

Sir Andrew Dillon, Nice chief executive, said he hoped Roche would "act in the best interest of patients" and use the consultation period to look again at their evidence and consider if there was "more" they could do.

"We had hoped that Roche would have recognised the challenge the NHS faces in managing the adoption of expensive new treatments by reducing the cost of Kadcyla to the NHS," he said.

"This drug is already being funded through the special Cancer Drugs Fund. Our job is to recommend whether it should transfer into the NHS budget.

"We are very aware of the importance that people place on life-extending cancer drugs and a decision not to recommend a cancer treatment for routine NHS funding is never taken lightly.

"We apply as much flexibility as we can in approving new treatments, but the reality is that given its price and what it offers to patients, it will displace more health benefit which the NHS could achieve in other ways, than it will offer to patients with breast cancer."

Professor Paul Ellis, consultant oncologist, at King's College, London and lead triallist for the drug in the UK, described the Nice draft guidance as a "huge blow".

"Kadcyla represents a significant advance in HER2-positive breast cancer, so for Nice to issue negative preliminary guidance is a huge blow," he said.

"The drug tackles the disease in a different way to any other breast cancer medicine and provides women with valuable extra time with their families and loved ones - time that you cannot put a price on.

"Not only this, Kadcyla is also much better tolerated by women than current standard treatment options, causing much less in the way of traditional chemotherapy associated side effects."

Jayson Dallas, general manager, Roche Products Limited, said: "Roche is extremely disappointed that Nice has failed to safeguard the interests of patients with this advanced stage of aggressive disease.

"The extension to the Cancer Drugs Fund was welcome news for those in England, meaning patients in the UK are some of the first in Europe to be able access medicines like Kadcyla.

"With Nice currently consulting on guidelines for 'value-based assessment', it will be important that they arrive at a sustainable solution that builds upon the success of the CDF, and ensures that patients continue to have rapid access to much needed cancer medicines."

Kadcyla is currently given to breast cancer patients who have failed on conventional treatment with Herceptin and chemotherapy.

The drug is only suitable for patients with the defective Her2 gene and trial results have shown it can extend life by six months compared with treatment with two other drugs, lapatinib (Tyverb) and capecitabine (a type of chemotherapy).

Kadcyla is designed to penetrate cancer cells and destroy them from within and, b ecause its action is so precise, a normally toxic form of chemotherapy can be used.

Clinical trial results have shown that women on Kadcyla survived 30.9 months compared with 25.1 months for patients treated with lapatinib and capecitabine.

The Cancer Drugs Fund (CDF) was set up for patients in England to access drugs approved by doctors but which have not been given the go-ahead for widespread use on the NHS.

The scheme was set to run until March this year but David Cameron announced last September that the funding programme will run for a further two years to March 2016.

Breakthrough Breast Cancer said currently an estimated 1,500 women in Britain could benefit from Kadcyla every year.

Senior policy manager, Dr Caitlin Palframan, said: " The drug appraisal process in England, and the cost of drugs, must change if prospects for patients are going to improve.

"This is the third highly-effective breast cancer drug to be rejected by Nice on the basis of cost in the last year and we will be responding to this latest decision, as well as the wider proposed changes to Nice's drug appraisal process, in due course.

"Drug development and research is moving at a pace that the system can't seem to keep up with.

"Kadcyla is a very impressive drug that has been shown to extend life by up to six months in HER2-positive secondary breast cancer patients, and with more manageable side effects than alternative drugs.

"We are now looking to the Department of Health and the pharmaceutical industry to find a way to work together to bring the cost of expensive drugs down and put a sustainable system in place by which new treatments can be made available on the NHS on a routine basis."

Emma Pennery, clinical director at Breast Cancer Care said: " It's extremely disappointing news for those living with advanced breast cancer and their families that yet another treatment has not been recommended by Nice.

"Kadcyla can mean those facing limited treatment options live longer and with fewer severe side effects, such as being sick, vastly improving their quality of life.

"We recognise that decisions about approval of cancer drugs are based on many complex factors, but we are concerned by the increasing number of people we support telling us how anxious they are about being able to access treatments when they need them.

"Kadcyla offers people with HER2 positive advanced breast cancer a unique combination of chemotherapy and targeted therapy in one agent.

"We await the results of the consultation period and the final guidance from Nice and hope Kadcyla will become widely available for eligible patients."

A spokeswoman for Roche added that the company would be working closely with Nice as part of the consultation period before final guidance is issued.

She said Kadcyla costs £5,908.16 per month and in the key Phase III study of the drug, patients were treated for an average of 9.6 months at a cost of just under £57,000. But she added that every patient responds differently to treatment.